The present disclosure relates to a liquid crystal display device including a liquid crystal display element in which a liquid crystal layer is sealed between a pair of substrates having an alignment film on their opposing surfaces, and a method of manufacturing the liquid crystal display device.
In recent years, a liquid crystal display (LCD) has been widely used as a display monitor for a liquid crystal television receiver, a notebook type personal computer, a car navigation device or the like. This liquid crystal display is classified into a variety of display modes (schemes) according to a molecule arrangement (alignment) of liquid crystal molecules included in a liquid crystal layer sandwiched between substrates. For example, a TN (Twisted Nematic) mode in which liquid crystal molecules are aligned to be twisted in a state in which a voltage is not applied is well known as a display mode. In the TN mode, the liquid crystal molecules have positive dielectric anisotropy, i.e., a property of a dielectric constant of the liquid crystal molecules in a long axis direction is greater than that in a short axis direction. For this, the liquid crystal molecules have a structure in which the liquid crystal molecules are aligned in a direction perpendicular to a substrate surface while an alignment orientation of the liquid crystal molecules is sequentially rotated within a plane parallel to the substrate surface.
Meanwhile, a VA (Vertical Alignment) mode in which liquid crystal molecules are aligned perpendicular to a substrate surface in a state in which a voltage is not applied has attracted attention. In the VA mode, the liquid crystal molecules have negative dielectric constant anisotropy, i.e., a property of a dielectric constant of the liquid crystal molecules in a long axis direction is smaller than that in a short axis direction. The VA mode can realize a wider viewing angle than the TN mode.
In a liquid crystal display in such a VA mode, when a voltage is applied, the liquid crystal molecules aligned in a direction perpendicular to a substrate respond to topple in a direction parallel to the substrate due to negative dielectric constant anisotropy, thereby transmitting light. However, since a direction in which the liquid crystal molecules aligned in the direction perpendicular to the substrate topple is arbitrary, alignment of the liquid crystal molecules is disturbed due to the applied voltage, which becomes a factor that worsens a response characteristic to the voltage.
Thus, technology for regulating the direction in which the liquid crystal molecules topple in response to the voltage in order to improve the response characteristic has been studied. Specifically, there is technology for pretilting liquid crystal molecules using an alignment film formed by applying a linearly polarized light of an ultraviolet ray or applying an ultraviolet ray from a direction oblique to a substrate surface (optical alignment film technology). For example, technology for forming an alignment film by applying a linearly polarized light of an ultraviolet ray or applying an ultraviolet ray from a direction oblique to a substrate surface to a film formed of a polymer including a chalcone structure to crosslink a double bond portion in the chalcone structure is known as the optical alignment film technology (see Japanese Patent Application Laid-Open Publication Nos. Hei10-087859, Hei10-252646 and 2002-082336). There is additional technology for forming an alignment film using a mixture of a vinyl cinnamate derivative polymer and a polyimide (see Japanese Patent Application Laid-Open Publication No. Hei 10-232400). Further, technology for forming an alignment film by applying linearly polarized light having a wavelength of 254 nm to a film including polyimide to decompose a portion of the polyimide (see Japanese Patent Application Laid-Open Publication No. Hei10-073821) is also known. Further, as peripheral technology for the optical alignment film technology, there is technology for forming a film including a liquid crystal polymer compound on a film formed of a polymer including a dichroic photoreactive constituent unit such as an azobenzene derivative, which has been irradiated with linearly polarized light or oblique light, as a liquid crystal alignment film (see Japanese Patent Application Laid-Open Publication No. Hei 11-326638).
Further, a liquid crystal display device including a liquid crystal display element having a pair of alignment films provided on opposing surfaces of a pair of substrates, and a liquid crystal layer provided between the pair of alignment films and including liquid crystal molecules having negative dielectric constant anisotropy, wherein at least one of the pair of alignment films includes a compound in which a polymer compound having a crosslinkable functional group as a side chain is crosslinked or deformed, and the liquid crystal molecules are pretilted by the crosslinked or deformed compound, is known from Japanese Patent Application Laid-Open Publication No. 2011-095696.